The demands on wireless communication networks as a medium for communicating data has been steadily increasing due in part the exponential growth of mobile device users. In order to accommodate the increased amount of mobile device traffic on the wireless communication network, network operators have been forced to implement spectrum resource management techniques to more efficiently use the limited spectrum allocated to them. These efficient spectrum management techniques for wireless communication networks are often referred to as radio resource management (RRM).
Several RRM techniques that have been implemented include dynamic RRM techniques that actively adjust the communication parameters according to traffic load, quality, path loss and interference, among other characteristics. One such RRM technique is referred to as link adaptation in which the purpose of link adaptation is to determine the appropriate modulation and level of error correction coding that is applied to meet a specified error probability. In particular, link adaptation uses information on communication link quality that is obtained either from measurements or from reporting of the channel state information (CSI) by the receiver. Selection of the appropriate modulation and error correction coding for each mobile device allows the wireless communication network to efficiently utilize the spectrum according to wireless communication characteristics.
The amount of time to perform link adaptation for a mobile device is typically confined to a transmission time interval (TTI). The transmission time interval in a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system is 1 millisecond (ms). A transmission resource of 180 kHz in frequency within one TTI is referred to as a scheduling block (SB) in which, in 3GPP, a physical resource block (PRB) is half a TTI in time or a slot. Moreover, there are several modulation schemes to select from such as quadrature phase shift keying (QPSK), sixteen quadrature amplitude modulation (16QAM) and 64QAM. Each modulation scheme may also include several possible levels of channel coding in which the combination of modulation scheme and coding, i.e., Modulation and Coding Scheme (MCS), provide numerous choices for RRM.
However, link adaptation is not without limits. For example, scheduling and link adaptation typically have to be performed one queue at a time because only after SBs have been allocated to a mobile device are the remaining SBs available for the other queues known to the scheduler. A mobile device can have one or more associated queues thereby making the efficient scheduling of multiple mobile devices even more challenging. In other words, scheduling and link adaptation techniques take into consideration the unallocated scheduling blocks. As such, the number of mobile devices that can be scheduled in a transmission time interval is limited by the processing time required for link adaptation for one mobile device.
Moreover, the task of selecting the optimal MCS and SBs given the numerous choices is often time consuming and further limits the amount of mobiles devices that can be scheduled per transmission time interval. For example, a time consuming link adaptation technique may use over half of the transmission time interval to determine the optimum MCS for one mobile device such that link adaptation will not be performed for the other mobile devices because there is not enough time left in the TTI. Moreover, the scheduled mobile devices may not even use the total available bandwidth such that other mobile devices would have been scheduled if the link adaptation process had not consumed so much time. Even if the total available bandwidth is utilized, it is likely that the bandwidth is not utilized efficiently by the scheduled mobile devices.